It is a legal requirement in several countries for a residual current circuit breaker to be able to detect a sinusoidal residual current completely independently of the mains voltage and, if necessary, to trip. However, the function of residual current circuit breakers of this type is very limited. Additional demands on a residual current circuit breaker, such as reliably detecting smooth and/or pulsating DC residual currents, generally require a trip circuit which is dependent on the mains voltage in order to be implemented. In this case, however, it should be ensured that the required basic functions are furthermore fulfilled by the relevant residual current circuit breaker in the event of a failure of said trip circuit which is dependent on the mains voltage.
Residual current circuit breakers are therefore known which have both a trip circuit which is independent of the mains voltage and a trip circuit which is dependent on the mains voltage. However, in such residual current circuit breakers, it has proven problematic to ensure that the trip circuit dependent on the mains voltage is in fact also only in operation when said circuit is functioning correctly and that otherwise the trip circuit which is independent of the mains voltage is used.